Electrical measuring instrument.



NO. 845,995. PATENTED MAR. 5, 1907. A. 0. BENBGKE.

ELECTRICAL MEASURING INSTRUMENT.

APPLICATION FILED NOV. 28. 1905.

3 SHEETSSHEET l.

PATENTED MAR. 5, 1907.

v A. 0. BE'NEGKE. ELECTRICAL MEASURING INSTRUMENT.

APPLICATION FILED NOV.2B, 1905.

3 SHEETS-SHEET 2.

. AV, 12g 5."

No. 845,995. PATENTED MAR. 5, 1907.

v I A. 0. BBNEGKE.

' ELECTRICAL MEASURING INSTRUMENT.

APPLICATION FILED NOV. 28,1905.

3 SHEBTSSHBET 3- f yz e m P3 6. q Illlll'lhlllllll'mllll'lllllllzrwassziv i Q INVE TOR.

A TTORNE Y's 'ADELBERT o. BENEOKE, OF New UNITED STATES PATENT OFFICE.

K, NEVFTTERSEY, ASSIGNOR TO AMERI- OAN INSTRUMENT COMPANY, A CORPORATIONOF NEW JERSEY. ELECTRICAL ME ASURl NG INSTRUMENT.

Specification of Letters Patent.

Patented March 5, 1907.

Application filed November 28, 1905. Serial No. 289,406.

To all whom it may concern:

Be it-known that I, ADELBERT 0. BEN- ECKE, of Newark, ltssex county, NewJersey, have invented a new and useful Improvement in ElectricalMeasuring instruments, of which the following is a specification.

My invention relates to an electrical measuring instrument which isequally adapted for the measurement of direct currents as for themeasurement of alternating currents of any frequency and wave form,whose indications are neither affected by temperature changes, externalmagnetic fields, nor the inductlon effects of alternating currents, andwhich can be used either as voltmeter or as ampere-meter.

Figures 1, 2, and 8 illustrate the principle on wnich my invention isbased, and Figs. 3, 4, 5, and 7 are illustrations of such constructionsof the instrument as appear practical. Fig. 6 is a diagrammatic detail.

Similar letters of reference indicate like parts.

It is a well-known fact that when two long strips of different materialhaving different coefficients of expansion are rigidly connectedtogether lengthwise the body so formed will be bent under the influenceof any change in the temperature. In Fig. 1, A is such a body consistingof two strips a and b, for example, of silver and platinum. If one endof this body is fixed, the other end Will move to the dotted-lineposition if the temperature of the body is increased, because thecoefficient of expansion of silver is larger than that of latinum. Thedotted-line position depen s 'upon the temperature of the body A andwhen read on a calibrated scale S can serve as a measure of thattemperature. If the body A is an electrical conductor and an electricalcurrent is sent through the same, the instrument will serve to measurethe strength of this current, as the heating effect of an electriccurrent depends upon its strength. The indications of such an electricalmeasuring instrument would, however, be aflected by any change in theatmospheric temperature.

In Fig. 2 the same body A, composed of the two strips a and b of silverand platinum, respectively, is shown. The motion of its free end B underthe influence of temperature changes is transmitted by a simple transprefer to divide into two A B, which consists. also of a silver strip aand a platinum strip b; but while the silver strip a forms the left halfof the body A B it forms the right half of the body A B. If both bodiesare alike and subjected to the same temperature changes, it is evidentthat the point B will remain stationary on the scale S. If one of thebodiesfor example, A Bis heated by the passage of an electric currentthrough the same, the position of B on the scale b" will be a measurefor the strength of the current and will be independent from any changein the surrounding temperature. For the construction of electricalinstruments I prefer to employ the bodies A and AVin the form of flatspirals, which coil up or uncoil under the influence of the temperaturechanges. The body A B, through which the current to be measured is sent,I

Width, Fig. 6, which allows the leading in and out of the currentwithout any additional flexible conductors.

Figs. 3, 4, 5, and 7 illustrate four different modifications of theinstrument. the flat spirals A, B, and O is composed of two flat stripsof different materials having a different coefficient of expansion. Twocylindrical shafts P P are pivoted in such manner that their axis ofrotation form a straight line. One end of each of the spirals A B isrigidly fixed to the frame F of the instrument through the conductors ee, insulated from each other and from the frame by means of theinsulators i 01. Here the current connection is made to the spirals A-B,which are electrically connected at their other ends and attached to theshaft P. One end of spiral O is also either directly or by means of anabutment D connected to the shaft P, whereas its other end is connectedto the shaft P which also carries the pointer or index T of theinstrument. The three spirals are wound in such a manner that in caseonly the'spirals A B are heated they would turn the shaft P, andtherefore, also,the shaft P and the index T, in the direction of thehands of a clock, and in case only the spiral O is heated it would turnthe shaft P and the index T in a direction opposite to the hands of aclock. The dimensions of the three spirals are so proportioned that ifsubjected to the same temperature change they counteract and balanceeach other, so

Each of that the index T will not change its position in reference tothe scale S, which is rigidly connected to the frame F. At the points J,I rovide jewel-bearings, as of sapphire, for t e pivot ends of theshafts P P as shown.- These being of insulating material serve theadditional purpose of preventing any current leakage or possibleshort-circuitin of the current. It is to be' understood that the workingparts are to be inclosed in a suitable case, as E, having theglass-covered openin E over thescalo S and the index T. There theradiated heat due to an electric current passing through the spiral A Bis likely to affect the s iral C, I may mount upon the shaft P a dis Gof any nonconductor of heat, as a disk' of mica or of hard rubber.

The modifications illustrated in Figs. 3, 4, 5, and 7 difier from thatillustrated in Fig; 2 only in the specific arrangement of the spiralsand the location of the index T. the shaft P is divided and the twosections are rigidly'connected together by means of the U-shaped frameX, while the shaft P is mounted in the open part of the frame/Xinalinement with the shaft-sections P.- Inl this case the spiral C isconnected to the frame X by means of the abutment D. The s irals may becomposed of any material W atever so long as they possess the requisitedifference .in their coeflicients of expansion and so long as one ofsaid spirals possesses therequisite electrical conductiv- 1ty, and I donot for this reason confine myself to the use of metallic substances. Ifind hard rubber and ivory to work admirabl well but because of ease ofmanipulation prefer to use two metals from which to construct thespirals. If now the instrument is connectedup in an electrical circuit,the 'current passing into the instrument will traverse the conductor e,the spirals A B, and out by the way of the conductor e, and thusgenerate a temperature in the spirals the degree of which is afunctionof the current strength or potential in.

' C and thence to the index-pointer accordance with the quality of theinstrument as an ammeter or voltmeter, and thereby cause said s irals tocoil up or uncoil as the metal of arger expansion is outside or inside.This uncoilin tendency is transmitted through the shaft tothe s iral bwhich the voltage or amperage is indicateh upon the' calibrated scale S.v

, The principle of my invention mayfbe carried out by causing theelectrical current to pass through the strips which are connected withor carry the index, whilevthe scale is connected with or carried by thetempera-f ture-strip, as diagrammatically shown in Fig. 8. Changes 1natmospheric temperature act e ually upon both sets of strips a b, sothat w en properly "adjusted the index In Fig. 5

v and upon this shaft I secure the spiral bi-- will always register at0. When an electric current is directed through the strips connectedwith the index T, the heat generated thereby will be added to the normaltemperature of these index-strips, and therefore the' index willindicate, the proper degree of de flection upon the scale.

In Fig. 7 is illustrated in concrete form the embodiment of thisprinciple of operation. The conductor-wires e 6 lead into the spiralstrips, as heretofore described; upon the shaft P, which shaft alsocarries the counterbalanced index T. In alinenient with the shaft P, Imount the shaft P in jeweled bearings,

metallic strip C the exterior endofthis spiral strip being secured inany convenient manner to the frame of themachine. Upon the shaft P, 'Isecure the counterbalanced scale-support S said scale-support carryingat its-outer end the graduated scale S It should be here noted that thespiral strips B and O are oppositely coiled in Figs. 3, 4, and 5 andthat the corresponding. spiral strips in Fig. 7 are coiledin the samedirection. The

reason for this arrangement is clearly shown in the diagrammatic Figs. 2and 8. Inasmuch as the spiral strips are all of the same character andcondition, changes in atmospheric temperature will affect them equally,and when properly adjusted the index T will always point to 0. Changesin the temperature of the spiral strips connected with the conductors e6, due to the passing of the electrical current therethrough, affectonly the index T; but inasmuch as both sets of spiral strips areaffected by the atmospheric temperature in common the resultantdifference in deflection is due solely tothe effect of the electricalcurrent.

' The principle of theoperation of this lastdescribed structure is thesame as that involved. in the structures illustrated in Figs. 3,4,and5.

It is evident that an instrument constructed as described in thisspecification has all the advantages of the so-called hot-wireinstruments and that its indications will-be and fragile wire which isalways kept taut by the action of a spring has the effect that this finewire is constantly stretched, which of course must alter the'constant orcalibration of the instrument This disadvantage 1s entirely overcome bymy invention, inasmuch as the set of spirals A B are placed in tan- Idem relation to carry the current, While the spiral C is free from anycurrent influence and is affected only by changes in surround- I ingtemperature, being thus free-to counterl act the same temperaturechanges which afj feet the spirals A B.

I claim s 1. In an electrical measuring instrument, the combination oftwo shafts in alinement, a spiral strip composed of two metals havingdifferent coeflicients of expansion, secured to each of said shafts,means for passing an electrical current through one of said spirals tocause the same to be deflected and rotate said shaft, means fortransmitting such motion to the other shaft through the spiral stripsecured thereto, and means for measuring the degree of such rotation.

2. In an electrical measuring instrument, the combination of a frame, ashaft mounted in said frame, a pair of spirals secured to. said shaft,said spirals being composed of two different met ls havingdiiferent'coeflicients of expansion, means for passing an electriccurrent through said spirals and thereby produce a'change in temperaturetherein and a consequent rotation of said shaft, a second I therebyshaft in alinement with the first-named shaft, means for measuring thedegree of such rota tion, and means mounted upon said second shaft forcounteracting such changes of temperature in said spirals as are due tothe surrounding atmosphere.

3. In anelectrical measurin instrument, the combination of a frameprovided with two shafts in alinement, an index secured to one of saidshafts, spirals composed of different metals having differentcoeffi'cients of expansion, said spirals being coiled in oppositedirections around said shafts respectively, whereby changes insurrounding temperature will cause the deflection of one spiral tocompensate for the deflection of the other, d means for directing anelectric current through one of said spirals, to cause a relative changeof temperature therein, and thereby produce .a relative deflection ofthe other spiral, and'means for measuring the degree of such deflection.

This specification this 20th day of November, 1905. v

ADELBERT O. BENEOKE. Witnesses:

FREDK. C. FISCHER, C. A. ALLIsToN.

5 signed and witnessed

